Ceiling fans have long been recognized and used as an inexpensive way to provide movement of air within rooms of buildings. They are simple to use and install, safe, and inexpensive when compared to such alternatives as for example refrigerated and evaporative air conditioning units. They can often provide a surprisingly effective alternative to air conditioning as the air movement they generate can evaporate skin perspiration with a resulting cooling effect.
It is known to combine ceiling fans with lighting means, as firstly it is a common requirement to provide ceiling mounted light sources, and secondly it is convenient to provide a single power supply to operate a combined fan and light fitting.
It has also been known to provide ceiling fans with some form of folding or retracting blade arrangement. This has been done to improve the appearance of the fan when it is not operative, to avoid the collection of dust on the blades and ease cleaning of the blades.
There have also been very few examples of combined ceiling fan and light fittings with retracting blades. Le Velle has described three versions. U.S. Pat. No. 1,445,402 discloses a light fitting and ceiling fan in which blades move outwards under centrifugal force when the fan is switched on, and are retracted by springs when the fan is switched off. U.S. Pat. Nos. 1,458,348 and 2,079,942 disclose improved versions, in which (unlike the early version of U.S. Pat. No. 1,445,402) the inward and outward movements of the blades are synchronized. Synchronizing blade movement is important for preserving satisfactory balance of the rotating parts of the fan. A ceiling fan that is poorly balanced may tend to come away from its mounting to the ceiling (potentially presenting a danger), may be noisier than a properly balanced fan and is generally unsightly.
References in this specification to certain patents are not intended as or to be taken as an admission that anything therein forms a part of the common general knowledge in the art.
Combined ceiling fans and light fittings with retractable blades have failed to become popular despite offering the advantages of both combining lighting means and a fan and of providing retractable blades.
The retraction mechanism described by Le Velle In U.S. Pat. No. 1,458,348 appears to be difficult to set up to keep all blades in good synchronization, and may also have been difficult to keep in that condition, for example if the wires used to connect the blades stretched.
The different mechanism described in U.S. Pat. No. 2,079,942 has links that extend from each blade to a rotatable “synchronizing ring”, and is simple in principle. However, the parts count is quite high and the assembly is believed to be labour-intensive and to require some skill. Further, the parts do not lend themselves well to cheap modern production materials and methods. Moreover, reasonably accurate synchronization of the blades when they are partly extended appears difficult to achieve due to the effect of clearances between the links and the holes accommodating them in the blades and synchronizing ring. As ceiling fans tend to come up to operating speed and come to a stop quite slowly in practice, this it is believed can lead to periods of significant unbalance.
A further disadvantage of the arrangement of U.S. Pat. No. 2,079,942 is that the synchronizing mechanism including the synchronizing ring has to lie substantially above the fan motor, due to the mechanism geometry, so that achieving a compact design is difficult, especially if it is desired to use a fan motor of modern casing design.
It is an object of the present invention to at least alleviate the above disadvantages. A further object is to provide a combined ceiling fan and light fitting with enhanced performance, including in respect of air moving performance.